August 12, 2014

Image: NASA

'First Light' Spectra provided by OCO-2

Image: NASA

A-Train of Satellites

NASA's Orbiting Carbon Observatory has reached its operational orbit and has begun collecting scientific data as commissioning of the spacecraft and its sensitive instrument continues to prepare for an ambitious science mission. Launched on July 2 aboard a Delta II rocket, OCO-2 successfully completed its initial steps in orbit consisting of the deployment of the two power-generating solar arrays, the initiation of two-way communications with the ground and the acquisition of a stable three-axis attitude of the spacecraft. Over the first few hours in orbit, OCO-2 underwent initial checkouts, confirming that the craft was in a safe configuration with good power-generation and stable body rates. Following its initial checkout operations, OCO-2 began in-depth testing lasting several weeks as teams put the spacecraft through its paces to confirm all subsystems were working properly. Shortly into the mission, OCO-2 began orbit-raising maneuvers as part of a carefully planned procedure to put the observatory into its operational orbit. Starting out in a 685 by 698-Kilometer orbit, OCO-2 had to raise its orbit by a few Kilometers. OCO-2 operates from a Sun-Synchronous Orbit at an altitude of 705 Kilometers, inclined 98.2 degrees. The Sun-Synchronous Orbit has a Local Time of Descending Node of 13:36 local time. OCO-2 is part of the A-Train of satellites. The A-Train is a series of Earth/atmospheric observation spacecraft in the afternoon sun-synchronous orbit flying in identical orbits to pass over any given location in close succession so that data from a variety of sensors can be correlated to create advanced scientific data products. Arriving in its operational orbit on August 3, OCO-2 is now part of the A-Train, leading the way.All A-Train satellites (OCO-2, GCOM-W1, Aqua, CALIPSO, CloudSat and Aura) pass over the same location on Earth within 16 minutes of each other to collect coordinated data from the same locations on Earth to increase the scientific return of each of the missions. Once OCO-2 arrived in its final orbit, the spacecraft activated the cryocooler of its focal plane assembly to begin cooling the detectors to their operational temperature of -153°C to reduce dark currents and increase their sensitivity. The optical components of the telescope were also cooled down for operation at -6°C.

The crucial 'first light' test was performed on August 6 as the OCO-2 observatory acquired its very first data set while flying over central Papua New Guinea.

“The initial data from OCO-2 appear exactly as expected -- the spectral lines are well resolved, sharp and deep,” said OCO-2 chief architect and calibration lead Randy Pollock of JPL. “We still have a lot of work to do to go from having a working instrument to having a well-calibrated and scientifically useful instrument, but this was an important milestone on this journey.”

Over the coming weeks, OCO-2 will complete instrument commissioning and calibration activities to fully optimize the performance of the instrument. Routine science observations will get underway as part of commissioning so that the ground processing system can be checked and optimized for the science mission. Science Data products will be available before the end of the year via the Earth Sciences Data and Information Services Center at NASA Goddard.

The overall objective of the OCO-2 mission is to provide a global measurement of CO2 distribution including carbon dioxide sources and sinks. To accomplish that, OCO-2 does not directly measure sources and sinks. Instead, the mission detects the column averaged carbon dioxide mole fraction that builds the foundation of computer-based data assimilation that will infer the sources and sinks that are present. This requires OCO-2 to make measurements of the complete atmospheric column in the absence of clouds and aerosols. To achieve that, the spacecraft acquires densely-spaced samples with each frame covering about 3 square Kilometers (1.29 by 2.25km). Three samples are taken every second, each consisting of eight-spectra including the absorption lines of carbon dioxide and oxygen that can then be analyzed using complex data processing. Flying in a polar sun-synchronous orbit, OCO-2 provides global coverage at a repeat cycle of 16 days.

The mission will uncover the processes that control the distribution of carbon dioxide in the atmosphere, quantifying the sources (natural and man-made) that emit CO2 into the atmosphere and also study the sinks of carbon dioxide. The CO2 sinks are of great importance as they absorb about half the carbon dioxide emitted by human activities, but it is not known how long this reduction of CO2 can continue which has significant implications for the rate of the CO2 build-up and its impact on Earth’s climate.

OCO-2 – the Orbiting Carbon Observatory 2 is a NASA mission studying carbon dioxide in Earth’s atmosphere on a global scale for a better understanding of the carbon cycle, and the natural processes and human activities that have an effect on the abundance and distribution of CO2, the most important greenhouse gas. Tracking and quantifying CO2 sources and sinks on a global scale over time and will allow scientists to improve forecasts of climatic changes.

The mission will uncover the processes that control the distribution of carbon dioxide in the atmosphere, quantifying the sources (natural and man-made) that emit CO2 into the atmosphere and also study the sinks of carbon dioxide. The CO2 sinks are of great importance as they absorb about half the carbon dioxide emitted by human activities, but it is not known how long this reduction of CO2 can continue which has significant implications for the rate of the CO2 build-up and its impact on Earth’s climate.

OCO-2 uses the LEOStar-2 spacecraft bus manufactured by Orbital Sciences to facilitate a range of payloads with masses up to 150 Kilograms. The OCO-2 satellite carries a single instrument consisting of three high-resolution spectrometers to detect atmospheric carbon dioxide.

Overall, the spacecraft has a mass of 455 Kilograms and consists of a hexagonal primary structure that is 0.94 meters wide and 2.12 meters long providing the mounting structure for all satellite systems.

The OCO-2 instrument consists of three high-resolution imaging spectrometers, was designed and developed by Hamilton Sundstand Sensor Systems.

The OCO-2 instrument has a mass of around 131 Kilograms measuring 1.6 by 0.4 by 0.6 meters and requires 125 Watts of power. Overall, the instrument covers a 1.29 by 2.25-Kilometer footprint at nadir and is capable of acquiring eight cross-track footprints creating a swath width of 10.3 Kilometers.

The spectrometers measure the sunlight reflected by the surface of Earth meaning that the sunlight entering the instrument has passed though the atmosphere twice. Carbon dioxide and molecular oxygen absorb radiation at distinct energy levels or wavelengths. A spectrum of radiation that passed through the atmosphere will show a reduced amount of energy at those characteristic wavelengths when compared with pure sunlight. OCO-2 acquires spectra in three wavelength ranges with high spectral resolutions using detectors that are cooled by a cryocooler to achieve the required accuracy of the measurements.

The instrument consists of three long-slit imaging grating spectrometers sharing a common bore-sight and covering the following spectral bands: the Oxygen A-Band at 0.764 µm and two carbon dioxide bands at 1.61 and 2.06 µm. The three spectrometers feature a similar optical design and share a mounting structure to improve rigidity and thermal stability. All spectrometers share a single telescope.>>>Detailed Spacecraft, Instrument & Science Overview

July 2, 2014

NASA’s Orbiting Carbon Observatory has arrived in orbit to begin tracking global carbon dioxide after a long road into space. Born out of a launch failure in 2009, the OCO re-flight mission was challenged to re-build and fly a carbon-copy of the original spacecraft on a tight budget and time scale. OCO-2 is NASA’s first observatory dedicated to tracking carbon dioxide in Earth’s atmosphere to deliver long-awaited data for scientists and policy-makers.

The OCO-2 satellite enjoyed a flawless launch atop a United Launch Alliance Delta II rocket that lifted off from Space Launch Complex 2 at Vandenberg Air Force Base at 9:56 UTC on Wednesday. Arcing into a dark, moonless night over the Pacific Ocean, Delta II carried OCO-2 into its target orbit with spacecraft separation 56 minutes after liftoff to mark the beginning of OCO’s ambitious mission.

Wednesday’s launch also marked the comeback of the venerable Delta II rocket after the workhorse did not see a launch for over two and a half years. Delta II is set for a handful missions including the OCO-2 launch, marking a short reprise for the launcher that will make three more NASA launches over the next two years with one vehicle still up for grabs.

Tasked with tracking atmospheric carbon dioxide on a global scale, OCO-2 will follow the carbon cycle, and the natural processes and human activities that have an effect on the abundance and distribution of CO2, one of the most important greenhouse gases that has significant effects on Earth’s climate.

“Carbon dioxide in the atmosphere plays a critical role in our planet's energy balance and is a key factor in understanding how our climate is changing,” said Michael Freilich, director of NASA’s Earth Science Division. “With the OCO-2 mission, NASA will be contributing an important new source of global observations to the scientific challenge of better understanding our Earth and its future."

Photo: NASA Kennedy

The mission will uncover the processes that control the distribution of carbon dioxide in the atmosphere, quantifying the sources (natural and man-made) that emit CO2 into the atmosphere and also study the sinks of carbon dioxide. The CO2 sinks are of great importance as they absorb about half the carbon dioxide emitted by human activities, but it is not known how long this reduction of CO2 can continue which has significant implications for the rate of the CO2 build-up and its impact on Earth’s climate.

Teams were able to support a quick turnaround of the Delta II rocket after Tuesday's launch attempt was scrubbed due to a faulty valve in the Water System of the launch pad. The suspect valve was removed and replaced with a spare to allow teams to re-start launch preparations later on Tuesday. Waiting for liftoff atop its Delta II rocket OCO-2 was set for several hours of countdown operations getting underway in the afternoon hours, local time.

Photo: NASA

Photo: NASA

For the launch of OCO-2, Delta II flew in its 7320 configuration consisting of a two-stage stack with a Kerolox first stage powered by an RS-27 engine, three GEM-40 solid rocket motors clustered around the first stage, and a hypergolic upper stage powered by an AJ-10-118K engine. The vehicle stands 38.9 meters tall with a core diameter of 2.44 meters and a launch mass of 152,000 Kilograms.

Still enclosed by its Mobile Service Tower, Delta II’s first stage completed Kerosene loading before teams started close-outs of the launch vehicle. Access platforms were removed and engineers buttoned up the launcher for the rollback of the MST that started at 0:35 UTC - with more the nine hours to go until liftoff.

Slowly moving to its launch position at a safe distance to the launch vehicle, the Mobile Service Tower cleared the way for liftoff. After MST rollback was complete, engineers started securing it for liftoff and close outs of the launch pad were started at SLC-2 as workers removed the access platforms at the base of the Delta II. Final preparations for propellant loading were made as teams completed the last hands-on tasks at the pad. Roadblocks were set up before the evacuation of the launch zone started around 4.5 hours before launch.

The launch team reported to console at L-4 hours and 20 minutes in readiness for the Terminal Countdown Operation. First on the agenda for all teams was a series of communication checks between the various support stations – the ULA launch team, the NASA/Orbital Sciences spacecraft team and the Western Range. The next step was the pressurization of helium and nitrogen systems of the pad to 1100psi for pressure vessel charging and purge setup.

At T-2 hours and 30 minutes, the countdown clock was initialized, starting with a one-hour built in hold filled with ground system preparations and checkouts before teams were polled to head into the Terminal Countdown Operation three hours before launch.

As soon as clocks started ticking, the Launch Team opened the countdown checklist, beginning with the activation of the RIFCA, Redundant Inertial Flight Control Assembly, the primary Guidance, Navigation and Control system of the Delta II launch vehicle. Following power-up, RIFCA went through extensive flight control system checkouts and various other systems also started testing including the electric, propulsion, communication and Flight Termination System.

Purge flow to the launch vehicle was set up and teams started launching weather balloons to monitor conditions in the upper atmosphere. Weather conditions at Vandenberg were perfectly fine for launch with no concerns heading into the countdown.

When the countdown reached L-2 Hours, the members of the launch team completed final preparatory tasks for Liquid Oxygen load on the first stage that started at L-1 hour 45 minutes after polling of the team was completed. The LOX tank of the first stage was the only propellant tank to be loaded during the countdown since the Kerosene tank on the first stage was loaded ahead of the countdown and the second stage was filled with storable propellants last week.

Pressing into LOX load, the transfer lines and 1st stage tank were chilled down before the –183°C oxidizer started flowing into the tank. While LOX was loaded, Delta II underwent C-Band transponder beacon checks.

It took just 30 minutes to fully load the LOX tank to the 100% level. At the 100% level, the LOX system on the first stage completed a test that included cycling the propellant fill&drain and safety valves before pressurizing the tank to ensure its integrity. After the test, LOX was allow to boil off to the 95% level.

Standing on its pad, fully fueled, Delta II was holding 96,120 Kilograms of propellant in its first stage and 6,000kg of hypergolics in the 2nd stage tanks along with Helium tank pressurant and Nitrogen attitude control system propellant.

After cryo load, teams initiated the activation and pressurization of the hydraulics system for pressure checks before the engines of the first and second stage were put through gimbal checks. Starting the final countdown hour, Delta II finished a last round of communication checks and Flight Termination System open loop tests. Nitrogen and Helium tank charging wrapped up as well and LOX was replenished to 95%. At T-15 minutes, the countdown entered a 20-minute built-in hold during which the launch team caught up with any open items and received a weather briefing.Counting down from T-15 to T-4 minutes, Delta II received the final version of its flight software, the Range Safety System Command Receiver underwent final checks and the RP-1 tank of the first stage was pressurized. LOX was topped up to 99% at L-17 minutes and the final weather verification took place at L-16 minutes.

Photo: NASA

Photo: NASA TV

Holding the countdown for ten minutes at T-4 allowed the spacecraft team to transition OCO-2 to battery power and switch it to flight mode. During the hold, the launch team was polled for a GO/No GO for the automated countdown sequence. All stations reported a GO, giving the final clearance to head into the Automated Countdown Sequence - a highly choreographed sequence of events that transition Delta II to its launch configuration.

Picking up the countdown at T-4 Minutes, Delta II started the transfer to internal power. After activation of the range safety system, the ordnances on the launch vehicle and the ignition system of the three GEM-40 Solid Rocket Motors were enabled. Fuel tank pressurization for flight started at T-3 minutes and the RP-1 umbilical was purged. At the same time, heaters on the launcher were shut off.

Two minutes ahead of launch, the LOX tank of the first stage started pressurization and top-off to 100% which was completed by T-30 seconds when the LOX system was isolated from the Ground Support Equipment. A final hydraulics test was performed 90 seconds before launch followed by the ‘all-clear’ from the Western Range and the handoff to Delta II’s flight computers at T-1 minute. A Green Board was verified at T-13 seconds ahead of the arming of the ignition system of the first stage and the GO for main engine start.

The RS-27 main engine of the first stage ignited at T-3 seconds, soaring up to its full launch thrust of 90,750-Kilogram force. When RS-27 reached stable operating conditions, the flight computers issued the ignition command to the three GEM-40 solid rocket motors. With a total launch thrust of 243,400 Kilogram-force, Delta II jumped off its pad, emerging from a cloud of smoke from booster ignition.

Liftoff occurred at precisely 9:56:23.272 and Delta II climbed vertically for a few seconds before starting to pitch and roll to get aligned with its launch azimuth of 196 degrees, flying south-west toward a polar orbit.

Delta II passed Mach 1 at T+36 seconds and encountered Maximum Dynamic Pressure 50 seconds into the flight powered by the RS-27 first stage engine and the three SRMs each delivering 50,800kgf of thrust, on average. Chamber pressure and thrust on the solids began to decline 63 seconds after launch as the GEM-40s burned out as planned after consuming 11,700kg of propellants each. To ensure a safe off-shore impact of the SRMs, Delta II held onto them until T+1:39 when pyrotechnics were fired to jettison the three ground-lit boosters at an altitude of 32 Kilometers as the vehicle was traveling at 800m/s.

With the solid rocket motors gone, Delta II continued propulsive flight on the first stage and its RS-27 engine alone that provided 107,500kgf of thrust with two 500kgf LR-101 sustainer engines used as verniers for roll control while RS-27 gimbaling was used to control the pitch and yaw attitude.

Burning 365 Kilograms of propellants per second, the first stage showed a nominal performance with very little control needed on the engines as the vehicle was sticking right to the calculated flight profile. The RS-27 engine of the first stage was shut down four minutes and 24 seconds into the flight after helping boost the vehicle to an altitude of 105 Kilometers and a speed of 4.97 Kilometers per second. For six seconds after MECO, the LR-101 engines continued to fire at a thrust of 380kgf each to dampen transients after RS-27 cutoff.

Following Vernier Engine Cutoff, the pyrotechnic stage separation was commanded at T+4:32 as the connection to the first stage was cut and the stage was pushed away by springs. The second stage ignited six seconds after stage separation.

With a total thrust of 4,425 Kilograms, the second stage’s AJ-10-118K was set for a burn of five minutes and 43 seconds to reach an elliptical Parking Orbit. The engine of the second stage consumed 14kg of Nitrogen Tetroxide and Aerozine 50 propellants per second to boost the speed of the vehicle by 2.5km/s to reach orbital velocity. Just after passing T+5 minutes, Delta II jettisoned its payload fairing, exposing the OCO-2 satellite hidden underneath for the rest of the way into orbit. Fairing separation took place at an altitude of 132 Kilometers when aerodynamic forces were no longer a danger to the spacecraft.

Photo: NASA TV

Photo: NASA TV

Photo: NASA TV

Shutdown on the second stage occurred just before reaching the T+10.5-minute mark in the flight. The stack reached a Parking Orbit of 185.2 by 727 Kilometers at an inclination of 98.141° which was very close to the target of 185 by 726 Kilometers, also matching in inclination.

In this Parking Orbit, the vehicle was set for a 40.5-minute coast to be able to reach the apogee of the orbit so that the second burn could serve as a circularization maneuver. Throughout the coast, Delta II conducted attitude maneuvers for thermal regulation using the cold gas reaction control system.

As the long coast approached completion, the second stage re-oriented for its second burn. Ignition of the AJ-10 engine occurred at T+50 minutes and the firing achieved the planned duration of just 12 seconds to boost the perigee of the orbit and slightly reduce the apogee. The vehicle ended up in an 685.2 by 697.5-Kilometer orbit at an inclination of 98.196 degrees compared to the target of 685 by 698 Kilometers, providing OCO-2 with a precise orbital insertion.

Photo: NASA TV

Capture of Spacecraft Separation (looking into the sun)

Following completion of the burn, the second stage maneuvered to the correct orientation for the separation of OCO-2. A camera installed on the upper stage showed the separation of the spacecraft 56 minutes after launch. Released into orbit, OCO-2 is embarking on a long-awaited mission of tracking carbon dioxide with never-before-seen accuracy and coverage.

The Delta II upper stage had two more burns on its flight plan beginning after a collision and contamination avoidance maneuver to boost itself into a disposal orbit. The first burn was expected to have a duration of 39 seconds starting at T+1 hour 25 minutes followed by a 51-second firing at T+1:56:40 to enter an orbit of 2,380 by 10,336 Kilometers.

For OCO-2, separation from Delta II marked the start of a pre-programmed sequence of events. The spacecraft successfully established communications with TDRSS, initiated an attitude stabilization maneuver and started the deployment of its two solar arrays. A good array deployment was confirmed by the spacecraft team marking a major step in the mission as OCO-2 was power-positive, re-charging its batteries via the solar arrays. The satellite is now set for about two weeks of commissioning to prepare the observatory for regular data acquisition.

July 1, 2014

Photo: NASA

The launch of NASA’s OCO-2 carbon dioxide mapping satellite atop a ULA Delta II rocket has been re-set for Wednesday after teams had to scrub Tuesday’s launch attempt due to a faulty Pad Water System. Repairs on the system were completed in time to permit a launch attempt at 9:56:23 UTC on Wednesday after a 24-hour turnaround.

Tuesday’s countdown was halted 46 seconds before launch when instrumentation on the launch pad showed that the Pulse Suppression Water System did not have a nominal water flow. After the launch attempt was scrubbed and Delta II was de-tanked, engineers accessed the pad to investigate the problem.

It was found that a faulty valve was the culprit, preventing water to flow as part of the system that dampens shockwaves and protects the pad from the high temperatures at launch. The valve had been tested ahead of the countdown and worked fine, but for some reason was not behaving in the final minutes of Tuesday’s launch attempt. Engineers removed the valve and replaced it with a spare that then completed testing.

Delta II enjoyed the day protected by its Mobile Service Tower that was moved back in place to provide access to the vehicle along with work platforms that were re-installed. Teams will re-initiate launch preparations in the afternoon hours local time when Delta II will receive its first stage fuel load as the tanks of the stage are filled with Rocket Propellant-1, highly refined Kerosene. Afterwards, Delta II will be closed out for flight before the Mobile Service Tower begins its rollback around nine hours before T-0 to clear the Delta II for Terminal Countdown Operations.

When the Mobile Service Tower is in its
launch position, at a safe distance to the Delta II, teams will make
final close outs of the launch pad by removing the launch mount access
platforms and buttoning up the Service Tower ahead of the evacuation of
the launch zone later in the countdown.

Four hours before the planned T-0 time, the launch team will report to console as the Countdown Clock is initiated at T-2 hours and 30 minutes, starting with a 60-minute built in hold. This countdown hold allows teams to complete setup tasks such as communication checks between the individual launch support stations and the preparation of ground systems for upcoming countdown operations. Before clocks start ticking, the process of evacuating the launch pad at SLC-2 will begin.

Delta II 7320 uses the standard two-stage stack of the Delta II
rocket with three GEM-40 Solid Rocket Motors clustered around the first
stage. The vehicle stands 38.9 meters tall with a core diameter of
2.44 meters and a launch mass of 152,000 Kilograms. The first stage of the Delta II is 26.1 meters long with a launch mass of 101,800 Kilograms including 96,120kg of Kerosene and Liquid Oxygen propellants. It is powered by a single RS-27 main engine delivering 1,054kN of vacuum thrust with engine gimbaling used to provide pitch and yaw control. Two 4.4kN LR-101 sustainer engines are used for roll control.

Each of the three GEM-40 SRMs is 11 meters long and 1.03m in diameter filled with 11,766kg of solid propellant that is used to deliver an average thrust of 499kN with a peak at 644kN.

The second stage of Delta II is 5.97m in length and weighs 6,950kg at launch using a single AJ-10-118K engine that delivers 43.4kN of vacuum thrust with re-start capability. The stack is topped with a payload fairing that is three meters in diameter and 8.5 meters long, protecting the OCO-2 spacecraft during atmospheric flight.At T-2 hours 30 minutes and counting, the RIFCA, Delta II’s brains, will be activated for pre-launch checkouts and software load. Helium and Nitrogen system pressurization is expected to begin around the same time and teams will put the Delta II through a series of electrical, communication system, Flight Termination System and propulsion system checkouts.

Photo: NASA Kennedy

>>>Delta II Countdown Timeline Starting at L-2 Hours, the launch team will go through polling for a GO/No GO for Liquid Oxygen loading – the only propellant component that has to be loaded during the countdown as RP-1 and second stage propellants will already be on board. LOX load starts at L-1 hour 45 minutes (8:11 UTC) beginning with the pressurization and chilldown of transfer lines and the 1st stage tank before the –183°C LOX starts flowing inside the vehicle. It takes about 30 minutes for LOX to be loaded to the 100% level to enable a test of the first stage propellant system – cycling the various valves and pressurizing the LOX tank to confirm its integrity. When the test is complete, Liquid Oxygen will be dumped to the 95% level.

Shortly after LOX load completion, Delta II will undergo hydraulic system activation and pressurization for pre-flight testing of the Thrust Vector Control System at L-56 minutes as the first and second stage engines are put through engine gimbal checks. Open Loop Testing of the Flight Termination System is finished 50 minutes before launch and a final round of communication checks with Delta II will be completed afterwards.

Helium and Nitrogen will be topped-off as the countdown enters a 20-minute built in hold at T-15 minutes (L-45 minutes). This hold allows teams to catch up with any open items and start preparing for the Automated Countdown Sequence. When the countdown resumes at L-25 minutes, LOX will be topped up to 95% again and Range Safety Checks will commence. A refined version of the flight software will be loaded into RIFCA based on the latest measurements of conditions in the upper atmosphere. At L-17 minutes, LOX will complete topping to 99%.

Photo: NASA

*File Image* - Photo: NASA

Entering the final built-in hold at T-4 minutes, the launch team has ten minutes to complete the final polls for the Automated Countdown. Also during the hold, OCO-2 transitions to battery power and enters flight mode to be ready for liftoff. Final clearance from the spacecraft team will be given at L-6 minutes. Purge pressures will be verified before the countdown resumes at 9:52 UTC.

Once clocks start ticking down from T-4 minutes, Delta II will start its Automated Countdown Sequence to make the final reconfigurations needed before launch. The sequence starts with the arming of the Range Safety Systems and the transfer of the two stages of Delta II to battery power. Ordnances on the launcher will be armed and the ignition system of the three solid rocket motors is enabled as well. Three minutes before launch, the RP-1 tank of the first stage pressurizes to flight level and the fuel umbilical is purged. Pressurization of the LOX tank starts at T-2 minutes as the tank finishes topping at 100% before being pressurized using ground supply pressure until T-30 seconds when LOX fill&drain valves are closed.

90 seconds before launch, Delta II undergoes a final hydraulic pressure verification followed by a last check with the Western Range to get final clearance for liftoff. As the countdown enters the last minute, Delta II assumes control of the final countdown steps using its own computers. A green board will be verified at T-13 seconds and the ignition system of the first stage is armed at T-10 seconds.

Three seconds ahead of liftoff, the RS-27 main engine ignites, soaring up to its full thrust of 90,750 Kilogram-force. When the engine reaches operational conditions, Delta II issues the command to ignite the three Solid Rocket Motors at the moment of T-0.

Jumping off its launch pad with a total thrust of 243,400 Kilogram-force, Delta will ascend vertically for a few seconds before making its pitch and roll maneuver to begin heading south-west on its way to a polar Sun-Synchronous Orbit. The vehicle will pass Mach 1 about 36 seconds after launch followed ten seconds later by Maximum Dynamic Pressure.

Thrust on the Solid Rocket Motors will start tailing off at T+63 seconds, but Delta II will hold onto the SRMs until T+1:39 to ensure a safe off-shore impact of the spent rocket motors. The first stage will continue burning its RS-27 engine until T+4 minutes and 24 seconds. After MECO at an altitude of 105 Kilometers and a speed of 4.97km/s, the LR-101 sustainer engines will continue burning for six more seconds before VECO – Vernier Engine Cutoff.

Staging between the first and second stage occurs at T+4:32 as pyrotechnics severe the mechanical connection in between the stages and springs push the stages apart to allow the AJ-10 engine of the upper stage to ignite at T+4 minutes and 38 seconds.

Delivering 4,425 Kilogram-force of thrust, the second stage will fire its engine for 5 minutes and 43 seconds to reach an elliptical parking orbit.

Five minutes and one second after launch, the vehicle will reach an altitude of 133 Kilometers, where payload fairing jettison will occur since aerodynamic forces can no longer harm the OCO-2 satellite.

>>>OCO-2 Ascent Overview Second stage cutoff is expected at T+10 minutes and 21 seconds, targeting an orbit of 185 by 726 Kilometers at an inclination of 98.1 degrees. To coast all the way up near the apogee of the orbit, the second stage will complete a 40-minute 29-second coast phase setting the stage for the circularization maneuver. The second burn of the upper stage will be very short with a planned duration of 12.4 seconds, scheduled to start at T+50:50. This burn will boost the vehicle into an orbit of 685 by 698 Kilometers at an inclination of 98.2 degrees for spacecraft separation. Following SECO-2, the second stage re-orients to achieve the correct attitude for OCO-2 separation at T+56 minutes and 15 seconds.

Image: NASA

Being sent on its way, OCO-2 will execute a pre-programmed sequence to establish a stable attitude, begin communications with the ground and unfold its two power-generating solar arrays. Solar Array deployment is expected to take up to ten minutes after which teams will confirm that the satellite is power-positive, marking the firs big milestone of spacecraft commissioning in orbit that will continue for several weeks before OCO-2 can start mapping atmospheric carbon dioxide.

For the Delta II second stage, the mission will continue for one more hour to complete an avoidance maneuver followed by a 39-second engine burn at T+1:25:00 and a 51-second firing at T+1:56:40 to reach a disposal orbit of 2,380 by 10,336 Kilometers.

﻿Delta II Launch with NASA's OCO-2 Satellite scrubbed by Pad Problem﻿

July 1, 2014

The launch of a United Launch Alliance Delta II rocket with NASA’s OCO-2 spacecraft was scrubbed in the last minute of the countdown on Tuesday when a technical problem with the launch pad water system emerged. Due to the short launch window of the mission, there was no time to recycle the countdown and the launch team had to call a scrub.

Tuesday’s launch countdown was uneventful leading up to the day’s launch opportunity at 9:56:44 UTC – a window stretching just 30 seconds due to the strict requirements of the targeted Sun-Synchronous Orbit of the OCO-2 spacecraft.

Still enclosed by its Mobile Service Tower, Delta II’s first stage completed Kerosene loading Monday afternoon before teams started close-outs of the launch vehicle which already had its second stage loaded with propellants last week. Access platforms were removed and engineers buttoned up the launcher for the rollback of the MST that started at 3:10 UTC after some delays that did not impact countdown operations.

Photo: NASA

The launch team reported to console at L-4 Hours to initiate the Terminal Countdown that started at T-2 hours 30 minutes with the activation of the Flight Control System of the Delta II rocket that was subsequently put through extensive testing along with all other critical subsystems of the Delta II rocket.

The only propellant tank to be filled during the launch countdown was the Liquid Oxygen Tank of the first stage with LOX load commencing at L-1 hour and 45 minutes and taking just 26 seconds to complete. Going through their final testing and reconfiguration activities after fueling, the Launch Team was tracking no issues as Delta II was well-behaved, the weather was favorable for launch and no ground systems issues were present.

Photo: NASA

Photo: NASA TV

Pressing into the final minutes of the countdown, the OCO-2 spacecraft transferred to internal power and the launch team cleared the Delta II rocket for the Automated Countdown Sequence beginning at T-4 minutes – a highly choreographed sequence of events that transition Delta II to its launch configuration.

Delta II continued to behave as it went through its final pre-launch steps that included the top-up of Liquid Oxygen, the pressurization of first and second stage tanks, the transfer to internal power and the arming of the ignition systems. Clocks continued to tick down inside one minute with no problems as Delta II assumed control of its final steps leading up to launch while the ground sequencer was in charge of the final ground systems operations that included the activation of the Launch Pad Water System.

At T-46 seconds, a hold was called in the countdown because engineers were receiving indications that the Pulse Suppression Water System did not show a nominal water flow. Delta’s Pulse Suppression System dumps water on the launch mount and associated ducts to dampen the shockwaves that occur during engine start and booster ignition and also protect the pad from the high temperatures occurring at liftoff. A good water system is a critical requirement for launch, leading to a hold if sensors show an off-nominal water flow.

After the hold was called, the Launch Team headed into Delta II safing operations to back out of the countdown and put the vehicle into a T-4-minute configuration by disabling ignition systems, re-activating heaters, venting the propellant tanks and re-initiating purge flow. Also, Delta II and OCO-2 were transferred back to external power.

Because this mission only has a 30-second launch window, any hold in the Automated Countdown will lead to an automatic scrub.

Scrubbing the launch attempt, teams began LOX de-tanking and the Nitrogen and Helium pressure vessels were also vented and started de-taking to safe the vehicle before engineers can access the launch pad. With a facility issue, the launch team did not have enough insight to determine what caused the bad water flow in the system – teams need to access the pad and inspect the system to find the problem.

Once engineers can get back to the pad, the Pulse Suppression System will be inspected and based on the findings of the team, a decision will be made on whether a 24-hour turnaround is possible or if more time is needed for repairs.

The Mobile Service Tower will be moved back into position and work platforms will be re-installed to allow technicians to access the launch vehicle. Teams will protect Wednesday’s launch opportunity by pressing into 24-hour turnaround operations until a decision on the next attempt is made when inspections have finished.

Wednesday’s launch window opens at 9:56:23 UTC and meteorologists are predicting a 100% chance of favorable weather conditions for the backup launch slot. Should a launch not be possible on Wednesday, teams will have to look at crew rest requirements before committing to a possible launch attempt on Thursday.

June 30, 2014

NASA and United Launch Alliance are ready for the launch of a ULA Delta II rocket on Tuesday, carrying the Orbiting Carbon Observatory 2 to orbit to begin a long-awaited mission of measuring atmospheric carbon dioxide with unprecedented accuracy. The green light for the 9:56 UTC launch was given on Sunday after a clean Launch Readiness Review.

The final set of launch preparations was initiated last Tuesday after the Flight Readiness Review gave the clearance for the propellant loading on the second stage of the Delta II rocket. Six metric tons of hypergolic propellants were filled into the tanks of the second stage last Wednesday and Thursday with Nitrogen Tetroxide oxidizer loading on Wednesday and Aerozine 50 fuel loading on Thursday. Due to the corrosive nature of these propellants, loading them puts a firm deadline on the launch as the second stage is only certified to launch within a specific time frame after fueling.

Last Wednesday, the ULA Launch Team and the OCO-2 spacecraft team participated in a full countdown and launch rehearsal that also involved the Delta II’s flight control system that was put through its paces one final time ahead of launch countdown operations. Final checks on the OCO-2 satellite were run on Friday.

Testing operations in progress on Sunday that included checks of the C-Band tacking link and the command receiver decoder of the Flight Termination System. Also, the final azimuth alignment of Delta II’s RIFCA was made – RIFCA, the Redundant Inertial Flight Control Assembly is the primary guidance, navigation and control system of the launcher.

Senior NASA and ULA managers met on Sunday to review the results of launch vehicle, spacecraft and ground systems testing to make sure all components that are necessary for mission success were ready to support the launch. No issues were found and the formal approval to press into launch operations was given.

Photo: NASA Kennedy

Tuesday’s launch window stretches precisely 30 seconds from 9:56:44 to 9:57:14 UTC, limited in duration due to the strict requirements of the target orbit of the OCO-2 spacecraft that takes the leading position of the A-Train of Earth Observation Satellites in Sun-Synchronous Orbit. Meteorologists are predicting a 100% chance of favorable weather conditions with no concerns for the early morning launch opportunity at 2:56 a.m. local time which may provide a sight for much of the western United States as Delta II will be visible from hundreds of Kilometers in a clear, moonless night.

﻿OCO-2 Flight Readiness Review complete ahead of Launch on Tuesday﻿

June 25, 2014

Photo: NASA Kennedy

Photo: NASA Kennedy

NASA and United Launch Alliance have successfully completed the Flight Readiness Review for the OCO-2 mission set for liftoff from Vandenberg at 9:56 UTC on Tuesday, July 1. The protective payload fairing was installed on the Delta II rocket this weekend to kick off final launch preparations as teams continue to work toward liftoff next week.

Last week, operations at Space Launch Complex 2 at Vandenberg Air Force Base continued with the installation of ordnances on the Delta II rocket on Wednesday and Thursday with associated testing being completed to make sure all pyrotechnics will work in flight. Meanwhile, teams closed out the OCO-2 spacecraft installed atop the Delta II second stage on June 14. Closeouts were in progress on Friday and Saturday as teams removed final protective covers from the spacecraft and made a last set of reconfigurations on the satellites ahead of the installation of the payload fairing.

On Saturday, the two halves of the protective payload fairing were installed around the OCO-2 satellite and attached to the Delta II rocket. Delta II’s payload fairing is nearly three meters in diameter and 8.5 meters long, offering enough space for the OCO-2 satellite to protect it while sitting on the launch pad and during atmospheric flight.

The Delta II rocket and OCO-2 satellite were also put through more countdown and launch simulations to ensure all systems are working properly and the Flight Control System issues the correct commands at the appropriate times. Final operations for the spacecraft will include battery charging and final electrical testing.

On Tuesday, ULA and NASA mission managers convened to conduct the Flight Readiness Review to confirm that the satellite, the launch vehicle and the Ground Support Systems are ready to support the launch of the OCO-2 spacecraft. No issues were identified except for minor items that will be closed out in time for the planned launch.

With the official GO given to proceed, the second Stage of the Delta II rocket is loaded with hypergolic propellants on Wednesday and Thursday. Nitrogen Tetroxide oxidizer is loaded on Wednesday and the Aerozine-50 fuel will be filled into the second stage’s tank on Thursday. Overall, Delta II’s second stage stands 5.97 meters tall and is 2.44 meters in diameter holding 6,000 Kilograms of hypergolics for consumption during flight by the AK-10-118K engine during flight to boost the OCO-2 spacecraft into orbit.

Friday and Saturday will see the final preparations of the Delta II launcher and its launch pad to set up for countdown and launch operations next week. On Sunday, the Launch Readiness Review will be performed to formally clear the Delta II for liftoff after a thorough review of the progress of launch preparations.

The weather outlook appears favorable for the launch attempt, but more accurate forecast models will be available closer to launch. Delta II countdown operations will get underway on Monday at SLC-2 when the Mobile Service Tower is rolled back to its launch position about nine hours before launch to uncover the Delta II rocket for its comeback mission after standing down for two and a half years. Terminal Countdown Operations begin four hours before liftoff, heading into Liquid Oxygen loading on the first stage one hour and 45 minutes before launch and the automated countdown sequence at T-4 minutes & counting to set the stage for blastoff.

﻿NASA Carbon Dioxide Mapping Spacecraft installed on Launch Vehicle﻿

June 16, 2014

After a long road to to launch, NASA’s Orbiting Carbon Observatory 2 has been installed on its Delta II rocket for liftoff on July 1 from Vandenberg Air Force Base, California. The original OCO mission launched in 2009, but the spacecraft never made it into orbit when its Taurus XL launcher suffered a payload fairing separation failure. After OCO was lost, studies were made for flying the OCO instrument as an integrated payload aboard a different platform or secure funding for a re-flight of the original design of the mission. Funding was secured in 2010 and construction was underway in 2011 and 2012 before testing started to allow OCO to make its way back to the launch pad.

As a key-component in NASA’S Earth observation strategy for the coming years, the loss of the OCO spacecraft had a number of impacts on the planned integrated observations between an inter-agency fleet of Earth observation spacecraft. By April 2009, the OCO mission team provided plans for a re-flight of a “carbon copy” of the original spacecraft within a few years if funding could be provided. The desire of establishing a reliable way of measuring carbon dioxide in Earth’s atmosphere and its potential implication for the scientific understanding of carbon dynamics prompted NASA and the U.S. government to secure funding for the re-flight of OCO-2

“Carbon dioxide in the atmosphere plays a critical role in our planet's energy balance and is a key factor in understanding how our climate is changing,” said Michael Freilich, NASA Earth Science director. “With the OCO-2 mission, NASA will be contributing an important new source of global observations to the scientific challenge of better understanding our Earth and its future."

OCO-2 will study carbon dioxide in Earth’s atmosphere on a global scale for a better understanding of the carbon cycle, and the natural processes and human activities that have an effect on the abundance and distribution of CO2, an important greenhouse gas. Tracking and quantifying CO2 sources and sinks on a global scale over time will allow scientists to improve forecasts of climatic changes.The mission will uncover the processes that control the distribution of carbon dioxide in the atmosphere, quantifying the sources (natural and man-made) that emit CO2 into the atmosphere and also study the sinks of carbon dioxide. The CO2 sinks are of great importance as they absorb about half the carbon dioxide emitted by human activities, but it is not known how long this reduction of CO2 can continue which has significant consequences for the rate of the CO2 build-up and its impact on Earth’s climate.

“Knowing what parts of Earth are helping remove carbon from our atmosphere will help us understand whether they will keep doing so in the future,” said Michael Gunson, OCO-2 project scientist.

Image: NASA/JPL

Photo: NASA Kennedy

“Understanding the processes controlling carbon dioxide in our atmosphere will help us predict how fast it will build up in the future. Data from this mission will help scientists reduce uncertainties in forecasts of how much carbon dioxide will be in the atmosphere and improve the accuracy of global climate change predictions.”>>>OCO-2 Spacecraft & Mission Overview

The launch contract for the OCO-2 mission was originally awarded in 2010 to Orbital Sciences Taurus XL with an expected launch date in 2013, but the contact was terminated when another Taurus XL experienced a launch failure and OCO-2 switched to United Launch Alliance’s Delta II rocket that will make a comeback for at least four missions beginning in 2014. Originally, Delta II entered retirement in 2011 after launching NASA’s GRAIL Twins and no morel launches on the manifest, however, components for five more Delta II rocket were available and NASA secured four of those launchers for missions in 2014 though 2016.

Photo: NASA Kennedy

Photo: NASA Kennedy

OCO-2 started assembly in 2010 as the bus of the satellite began integration at Orbital Sciences based on the flight-proven LEOStar-2 platform that was also used by the original OCO satellite. The instrument – a set of three high-resolution infrared spectrometers installed on a single telescope - started assembly at NASA’s Jet Propulsion Laboratory. The philosophy behind OCO-2 was to copy the design of OCO as close as possible to avoid re-certification or re-designs of components that would have consumed time and money the project did not have. Only minor changes were implemented due to the unavailability of parts that were out of production (the Cryocooler of the instrument’s Focal Plane) or the implementation of modern components with more capabilities, but the same satellite interfaces as the previous systems (e.g. star trackers).

The OCO-2 instrument finished construction in early May 2012 and was shipped to Orbital’s facility in Gilbert, Arizona where the OCO-2 spacecraft bus was already waiting, having been built by Orbital and shipped to Arizona earlier. The change from Taurus XL to Delta II added about nine months to the launch campaign and OCO-2 was booked for a longer stay in Arizona once integration and testing was complete. After the instrument was installed on the bus, five months of extensive testing began taking until late in 2012. These tests included functional tests of the spacecraft and instrument, vacuum testing, radio interference checks, vibration tests and a series of electrical checks – giving the craft a clean bill of health before being put in storage to wait for its launch opportunity. Re-testing was completed in late 2013.

At Vandenberg Air Force Base in California, the first components for the Delta II launcher started arriving in late 2013. First to arrive were the three GEM-40 solid rocket motors that were leak-checked and put into storage before the Delta II payload fairing was delivered in January 2014. In February, trucks arrived at Vandenberg bringing the Delta II’s Interstage Adapter and second stage. The core stage of the launcher arrived at the Building 836 hangar in mid-March.

All the components enjoyed a period of acceptance tests and general checkouts at the hangar before the fairing and second stage moved to the Horizontal Processing Facility at Space Launch Complex 2. On March 28, the 26.1-meter tall first stage was moved to the vertical position and installed on the launch table at SLC-2 enclosed in the Mobile Service Tower that provided access platforms for engineers. SLC-2W hadn’t seen a Delta II rocket in more than two and a half years, having supported the most recent Delta II launch from Vandenberg in October 2011 when DII launched the Suomi NPP weather satellite.

With the first stage vertical and secured on the launch mount, teams started installing the three Solid Rocket Motors on the first stage taking several days with the final SRM being installed on April 14.

In the following two weeks, the first stage received its interstage adapter and the second stage was hoisted above the vehicle to be mated with the stack to complete the initial integration of the launch vehicle in the last week of April. >>>Delta II Launch Vehicle Overview

On April 30, the OCO-2 spacecraft arrived at Vandenberg, being delivered to the Astrotech payload processing facility for several weeks of final launch preparations. Unpacked from its shipping container, OCO-2 first underwent a Limited Performance Test – an electrical checkout of the satellite and its different systems that was followed by a functional test of the propulsion system and necessary fueling preparations. The vehicle then received its propellant load of 45 Kilograms of hydrazine monopropellant.>>>OCO-2 Processing Photos

While OCO-2 was getting ready for launch, the Delta II was also being prepared for its comeback. After hydraulic testing and a set of electrical checks, Delta II and its launch team completed a Wet Dress rehearsal – conducting a full-duration countdown rehearsal involving the same procedures needed on launch day to allow the launch team to get up to speed on operations and also put the Delta II through testing.

Loading the first stage’s liquid Oxygen with the –183°C oxidizer confirmed that no leaks were present and all components showed a nominal performance during the test that was followed-up by the combined systems test in late May that focused on the flight control system of the Delta II launcher to ensure the commands sent by the controllers would reach the various actuators on the vehicle at the appropriate times. Last week, the launch vehicle completed a Rocket Propellant-1 tanking demonstration that confirmed the integrity of the fuel system and tank.>>>Delta II Integration Photos

OCO-2 was powered up on June 2-3 for a health check and testing of its reaction wheels needed for attitude control and pointing of its telescope once the vehicle arrives in orbit. Next, the spacecraft was closed out and completed final reconfigurations before being attached to its Payload Adapter on June 10 and making an overnight trip from the processing facility over to the launch pad on Saturday where it was hoisted up above the Delta II rocket to be carefully lowered on top of the second stage for installation.

After structural attachments were made, data and electrical connectors were mated as well to allow the OCO-2 and Delta II to exchange data during countdown and flight. As part of integrated testing, the stacked vehicle is set to complete a series of electrical tests, checkouts of the various data and flight control systems and combined checks of the launcher and payload as part of countdown and flight simulations.

The OCO-2 spacecraft will be closed out for flight this week in order for the two halves of the payload fairing to be installed on Friday. Leading up to launch, the Flight Readiness Review from a payload standpoint and the Launch Readiness Review for the launch vehicle will be completed.

Preparations remain on track for the launch of NASA’s OCO-2 satellite at 9:56 UTC on July 1, 2014 from Space Launch Complex 2W and Vandenberg Air Force Base.

Photo: NASA Kennedy

Delta II Second Stage

Photo: NASA Kennedy

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